Power generation system, driving method for power generation system, and combustor

ABSTRACT

In a power generation system, exhausted fuel gas exhausted from a solid oxide fuel cell (SOFC) is used as a fuel of a first combustor or a second combustor of a gas turbine, and at the same time, a part of compressed air compressed by a compressor of the gas turbine is used to drive the SOFC. The gas turbine includes the first combustor for burning fuel gas which is different from the exhausted fuel gas, a first turbine configured to be driven by combustion gas supplied from the first combustor, the second combustor for burning at least a part of the exhausted fuel gas, and a second turbine coupled with the first turbine and configured to be driven by combustion gas supplied from the second combustor.

FIELD

The present invention relates to a power generation system in which afuel cell, a gas turbine, and a steam turbine are combined, a drivingmethod for the power generation system, and a combustor.

BACKGROUND

A solid oxide fuel cell (referred to as SOFC below) as a fuel cell hasbeen known as a general-purpose and high-efficiency fuel cell. Since anoperating temperature of the SOFC is set to be high to increase an ionconductivity, compressed air discharged from a compressor of the gasturbine can be used as air (oxidant) supplied to a side of an airelectrode. Also, high-temperature exhausted fuel gas exhausted from theSOFC can be used as a fuel of the combustor of the gas turbine.

Therefore, for example, as described in Patent Literature 1, variouspower generation systems in which the SOFC, the gas turbine, and thesteam turbine are combined have been proposed as a power generationsystem which can achieve a high-efficiency power generation. In acombined system described in Patent Literature 1, the gas turbineincludes a compressor for compressing air and supplying it to the SOFCand a combustor for generating combustion gas from the exhausted fuelgas exhausted from the SOFC and the air.

For example, Patent Literature 2 discloses a fuel cell system includinga combustor for burning exhausted fuel gas to be exhausted from a fuelcell. The combustor includes a primary combustion chamber and asecondary combustion chamber. The exhausted fuel gas from the fuel cellis jetted from a burner, and the primary combustion chamber performsprimary combustion of the exhausted fuel gas by using primary air. Thesecondary combustion chamber is connected to the primary combustionchamber via a communication passage having a gas passage narrower thanthe primary combustion chamber and performs secondary combustion of thegas from the primary combustion chamber by using secondary air. Theburner includes triple blowoff port. In the triple blowoff ports, atorch flame blowoff port for jetting an ignition torch flame is arrangedat the center, and an annular exhausted fuel blowoff port for jettingthe exhausted fuel gas is arranged outside the torch flame blowoff port.Also, a circular exhausted air blowoff port for jetting exhausted air tooutside the exhausted fuel blowoff port is concentrically arranged. Theburner also includes a plurality of auxiliary fuel blowoff ports, whichpasses through the exhausted air blowoff port and jets the auxiliaryfuel, in the exhausted air blowoff port.

Also, for example, Patent Literature 3 discloses a fuel supply methodfor the combustor for supplying at least two kinds of fuels havingdifferent calories from each other to the combustor. At the time ofstarting operation of the gas turbine, a high calorie fuel and lowcalorie fuel are supplied to the combustor by using both a first fuelsupply system for supplying the high calorie fuel to a first nozzleincluded in the combustor and a second fuel supply system for supplyingthe low calorie fuel to a second nozzle included in the combustor. Whenan output of the gas turbine reaches the output which can realizecontinuous operation with the low calorie fuel, the supply of the highcalorie fuel to the combustor is interrupted, and the low calorie fuelis supplied to the combustor.

CITATION LIST Patent Literature

-   -   Patent Literature 1: Japanese Laid-open Patent Publication No.        2009-205930    -   Patent Literature 2: Japanese Laid-open Patent Publication No.        2008-166070    -   Patent Literature 3: Japanese Laid-open Patent Publication No.        2012-41882

Technical Problem

In a power generation system described in the above-mentioned PatentLiterature 1, a gas turbine is driven by combustion gas generated byburning exhausted fuel gas exhausted from a SOFC and compressed air in acombustor. On the other hand, the SOFC generates power by using suppliedfuel gas and compressed air compressed by a compressor and exhausts theexhausted fuel gas and the compressed air used to generate the power tothe gas turbine. Therefore, after the gas turbine has been driven first,the SOFC is driven by supplying the compressed air thereto.

In the power generation system described in the above-mentioned PatentLiterature 1, the combustor for supplying the combustion gas to the gasturbine needs the fuel gas because the exhausted fuel gas is notsupplied in a state where the SOFC is not operated. Also, when theexhausted fuel gas from the SOFC is used as a fuel, it is necessary forthe combustor to supplement the heat input by supplying the fuel gaswith high calorie in a case where the heat input is lacked relative tothe heat input in which the gas turbine reaches the rated load. In thisway, when the power generation system in which the SOFC, the gasturbine, and the steam turbine are combined is operated, fuels to besupplied to the combustor become different kinds from each other, suchas the exhausted fuel gas and the fuel gas, according to the operationstate of the SOFC and the gas turbine.

Generally, it is preferable to use a mixer to burn different kinds offuel gases in the combustor. However, the exhausted fuel gas exhaustedfrom the SOFC reaches about 400° C., and the fuel gas to supplement theheat input is about 15° C. The temperatures differ from each other.Therefore, there is a possibility that the respective fuel gases are notevenly mixed due to the difference in temperature and the combustionbecomes unstable in the mixer. Also, it becomes necessary to takemeasures against thermal expansion in the mixer and piping around themixer due to the difference in temperature.

SUMMARY

The present invention is to solve the above-mentioned problems. Apurpose of the present invention is to provide a power generation systemand a driving method for the power generation system which can solveinconvenience caused by a difference in temperature of the differentkinds of fuel gases.

The present invention is to solve the above-mentioned problems. Apurpose of the present invention is to provide a power generationsystem, a driving method for the power generation system, and acombustor which can drive the gas turbine in a stable state even whendifferent kinds of fuels are supplied to the combustor at the time ofdriving the power generation system.

Solution to Problem

According to a first aspect of the present invention in order to achievethe above purpose, there is provided a power generation system, whereinexhausted fuel gas exhausted from a fuel cell is used as a fuel of acombustor of a gas turbine, and at the same time, a part of compressedair compressed by a compressor of the gas turbine is used to drive thefuel cell, and the gas turbine includes a first combustor for burningfuel gas which is different kind from the exhausted fuel gas, a firstturbine driven by combustion gas supplied from the first combustor, asecond combustor for burning the exhausted fuel gas, and a secondturbine shaft-coupled with the first turbine and driven by thecombustion gas supplied from the second combustor.

Therefore, the exhausted fuel gas and the fuel gas are separately burnedin different combustors from each other. Therefore, it is not necessaryto mix the exhausted fuel gas and the fuel gas by the mixer. There is nocase where the respective fuel gases are not evenly mixed and thecombustion becomes unstable and where it is necessary to take measuresagainst the thermal expansion in the mixer and the piping around themixer due to the difference in temperature. Accordingly, theinconvenience caused by the difference in temperature of the differentkinds of fuel gases can be solved.

According to a second aspect of the present invention, there is providedthe power generation system according to the first aspect, including: aconnecting/disconnecting unit configured to connect or disconnect ashaft coupling between the first turbine and the second turbine.

Therefore, when a connecting/disconnecting unit is not included, sincethe second turbine is rotated together with the first turbine in a statewhere the combustion gas is not supplied to the second turbine at thetime of driving the first turbine, the load is applied to the firstturbine. However, a situation where the load is applied to the firstturbine can be prevented by having the connecting/disconnecting unit.

According to a third aspect of the present invention, there is providedthe power generation system according to the first or second aspect,including: a fuel gas supply line configured to supply the fuel gas tothe first combustor; an exhausted fuel gas supply line configured tosupply the exhausted fuel gas to the second combustor; a fuel gascontrol valve configured to be provided in the fuel gas supply line; anexhausted fuel gas control valve configured to be provided in theexhausted fuel gas supply line; and a controller configured to controlto close the exhausted fuel gas control valve and open the fuel gascontrol valve before the fuel cell is driven and control to open theexhausted fuel gas control valve after the fuel cell has been driven.

Therefore, when the gas turbine is driven, the first turbine is drivenby supplying the fuel gas to a first combustor. Also, after the firstturbine has been driven, the fuel cell is driven by supplying a part ofthe compressed air compressed by the compressor to the fuel cell. Whenthe fuel cell is driven, the exhausted fuel gas is exhausted from thefuel cell. Therefore, the exhausted fuel gas is supplied to a secondcombustor. In this way, a power generation system according to thepresent invention separately burns the exhausted fuel gas and the fuelgas in different combustors from each other. At the same time, the powergeneration system can efficiently drive the fuel cell.

According to a fourth aspect of the present invention in order toachieve the above purpose, there is provided a driving method for apower generation system, including: a process for driving a firstturbine by supplying fuel gas to a first combustor; a process forsubsequently driving a fuel cell; and a process for subsequently drivinga second turbine by supplying exhausted fuel gas to a second combustor,wherein the exhausted fuel gas exhausted from the fuel cell is used as afuel of a combustor of a gas turbine, and at the same time, a part ofcompressed air compressed by a compressor of the gas turbine is used todrive the fuel cell, and the gas turbine includes the first combustorfor burning fuel gas which is different kind from the exhausted fuelgas, the first turbine driven by combustion gas supplied from the firstcombustor, the second combustor for burning the exhausted fuel gas, andthe second turbine shaft-coupled with the first turbine and driven bythe combustion gas supplied from the second combustor.

Therefore, when the gas turbine is driven, the first turbine is drivenby supplying the fuel gas to a first combustor. Also, after the firstturbine has been driven, the fuel cell is driven by supplying a part ofthe compressed air compressed by the compressor to the fuel cell. Whenthe fuel cell is driven, the exhausted fuel gas is exhausted from thefuel cell. Therefore, the exhausted fuel gas is supplied to a secondcombustor. In this way, a driving method for the power generation systemaccording to the present invention separately burns the exhausted fuelgas and the fuel gas in different combustors from each other. Therefore,it is not necessary to mix the exhausted fuel gas and the fuel gas bythe mixer. There is no case where the respective fuel gases are notevenly mixed and the combustion becomes unstable and where it isnecessary to take measures against the thermal expansion in the mixerand the piping around the mixer due to the difference in temperature.Accordingly, the inconvenience caused by the difference in temperatureof the different kinds of fuel gases can be solved. In addition, adriving method for the power generation system according to the presentinvention separately burns the exhausted fuel gas and the fuel gas indifferent combustors from each other. At the same time, the drivingmethod for the power generation system can efficiently drive the fuelcell.

According to a fifth aspect of the present invention, there is providedthe driving method for the power generation system according to thefourth aspect, including: a connecting/disconnecting unit configured toconnect or disconnect a shaft coupling between the first turbine and thesecond turbine; a process for disconnecting the shaft coupling betweenthe first turbine and the second turbine by the connecting/disconnectingunit; a process for subsequently driving the first turbine by supplyingthe fuel gas to the first combustor; a process for subsequently drivingthe fuel cell; a process for subsequently connecting the shaft couplingbetween the first turbine and the second turbine by theconnecting/disconnecting unit; and a process for subsequently drivingthe second turbine by supplying the exhausted fuel gas to the secondcombustor.

Therefore, when a connecting/disconnecting unit is not included, sincethe second turbine is rotated together with the first turbine in a statewhere the combustion gas is not supplied to the second turbine at thetime of driving the first turbine, the load is applied to the firstturbine. However, a situation where the load is applied to the firstturbine can be prevented by having the connecting/disconnecting unit.

According to a sixth aspect of the present invention in order to solvethe above purpose, there is provided a power generation systemincluding: a controller configured to control to close a first mainnozzle control valve and open a second main nozzle control valve when agas turbine is started and control to open the first main nozzle controlvalve and restrict the second main nozzle control valve when a fuel cellis started after the gas turbine has been driven, wherein exhausted fuelgas exhausted from the fuel cell is used as a fuel of a combustor of thegas turbine, and the combustor includes a first main nozzle, a secondmain nozzle, a first main nozzle fuel line which is connected to thefirst main nozzle and sends the exhausted fuel gas exhausted from thefuel cell, a second main nozzle fuel line which is connected to thesecond main nozzle and sends a fuel gas different kind from theexhausted fuel gas, the first main nozzle control valve provided in thefirst main nozzle fuel line, and the second main nozzle control valveprovided in the second main nozzle fuel line.

Therefore, when the gas turbine is started, the gas turbine is startedby supplying the fuel gas to the combustor. Also, after the gas turbinehas been started, the fuel cell is started by supplying a part of thecompressed air compressed by the compressor to the fuel cell. When thefuel cell is started, the exhausted fuel gas is exhausted from the fuelcell. The exhausted fuel gas is supplied to the combustor, and at thesame time, a predetermined amount of the fuel gas of which a flow rateis restricted is supplied. In this way, the heat input shortage of theexhausted fuel gas is supplemented. Therefore, the power generationsystem can drive the gas turbine in a stable state. In addition, sincethe high-temperature exhausted fuel gas and the low-temperature fuel gasare respectively supplied from the first and second main nozzles and areburned, the mixer for mixing the exhausted fuel gas and the fuel gashaving different temperatures from each other and supplying it to thecombustor can be omitted.

According to a seventh aspect of the present invention, there isprovided the power generation system according to the sixth aspect,wherein the combustor includes a pilot nozzle, a pilot nozzle fuel linewhich is connected to the pilot nozzle and sends the fuel gas, and apilot nozzle control valve provided in the pilot nozzle fuel line, andthe controller controls to open the pilot nozzle control valve when thegas turbine is started and driven.

Therefore, when the gas turbine is started and driven, the fuel gasinjected from a pilot nozzle is burned. According to this, flame holdingcan be performed to perform stable combustion of the premixed gas inwhich the exhausted fuel gas and the fuel gas respectively injected fromthe first main nozzle and the second main nozzle is mixed with thecompressed air.

According to an eighth aspect of the present invention in order to solvethe above problem, there is provided a driving method for a powergeneration system including: a process for injecting fuel gas from onlya second main nozzle when a gas turbine is started; and a process forinjecting exhausted fuel gas from a first main nozzle and injecting thefuel gas restricted by a predetermined amount from the second mainnozzle at the same time when a fuel cell is started after the gasturbine has been started, wherein the exhausted fuel gas exhausted fromthe fuel cell is used as a fuel of a combustor of the gas turbine, andthe combustor includes the first main nozzle for injecting the exhaustedfuel gas exhausted from the fuel cell and the second main nozzle forinjecting the fuel gas which is different kind from the exhausted fuelgas.

Therefore, when the gas turbine is started, the gas turbine is startedby injecting the fuel gas from the second main nozzle of the combustorand burning it. Also, after the gas turbine has been started, the fuelcell is started by supplying a part of the compressed air compressed bythe compressor to the fuel cell. When the fuel cell is started, theexhausted fuel gas exhausted from the fuel cell is injected from thefirst main nozzle of the combustor, and at the same time, apredetermined amount of the fuel gas which supplements the heat inputshortage of the exhausted fuel gas is injected from the second mainnozzle. Therefore, the power generation system can drive the gas turbinein a stable state. In addition, since the high-temperature exhaustedfuel gas and the low-temperature fuel gas are separately supplied fromthe first and second main nozzles and are burned, the mixer for mixingthe exhausted fuel gas and the fuel gas having different temperaturesfrom each other and supplying it to the combustor can be omitted.

According to a ninth aspect of the present invention in order to achievethe purpose, there is provided a combustor included in a powergeneration system having a fuel cell and a gas turbine, including: afirst main nozzle configured to inject exhausted fuel gas exhausted fromthe fuel cell; a second main nozzle configured to inject fuel gas whichis different kind from the exhausted fuel gas; a first main nozzlecontrol valve configured to control injection of the exhausted fuel gasfrom the first main nozzle; and a second main nozzle control valveconfigured to control injection of the fuel gas from the second mainnozzle, wherein combustion gas in which the exhausted fuel gas exhaustedfrom the fuel cell is burned and supplied to the gas turbine.

Therefore, when the gas turbine is started, the gas turbine is startedby opening a second main nozzle control valve, injecting the fuel gasfrom the second main nozzle, and burning it. Also, after the gas turbinehas been started, the fuel cell is started by supplying a part of thecompressed air compressed by the compressor of the gas turbine to thefuel cell. When the fuel cell is started, the first main nozzle controlvalve is opened and the exhausted fuel gas exhausted from the fuel cellis injected from the first main nozzle and burned, and at the same time,a predetermined amount of the fuel gas of which the flow rate isrestricted by the second main nozzle control valve is injected.Accordingly, the heat input shortage of the exhausted fuel gas issupplemented. Therefore, the power generation system can drive the gasturbine in a stable state. In addition, since the high-temperatureexhausted fuel gas and the low-temperature fuel gas are respectivelysupplied from the first and second main nozzles and are burned, themixer for mixing the exhausted fuel gas and the fuel gas havingdifferent temperatures from each other and supplying it to the combustorcan be omitted.

According to a tenth aspect of the present invention, there is providedthe combustor according to the ninth aspect, further including: a pilotnozzle configured to inject the fuel gas; and a pilot nozzle controlvalve configured to control injection of the fuel gas from the pilotnozzle.

Therefore, when the gas turbine is started and driven, the pilot nozzlecontrol valve is opened and the fuel gas injected from a pilot nozzle isburned. According to this, flame holding can be performed to performstable combustion of the premixed gas in which the exhausted fuel gasand the fuel gas respectively injected from the first main nozzle andthe second main nozzle is mixed with the compressed air.

Advantageous Effects of Invention

According to the present invention, the inconvenience caused by thedifference in temperature of the different kinds of fuel gases can besolved.

According to the present invention, when the power generation system isdriven, the gas turbine can be driven in a stable state even whendifferent kinds of fuels are supplied to the combustor.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic block diagram of a power generation systemaccording to a first embodiment of the present invention.

FIG. 2 is a timing diagram of the power generation system according tothe first embodiment at the time of driving.

FIG. 3 is a schematic diagram of a combustor of a power generationsystem according to a second embodiment of the present invention.

FIG. 4 is a cross-sectional diagram along the line A-A in FIG. 3.

FIG. 5 is a flowchart of fuel supply in the power generation system ofthe second embodiment at the time of driving the combustor.

FIG. 6 is a schematic block diagram of the power generation systemaccording to the second embodiment.

DESCRIPTION OF EMBODIMENTS First Embodiment

Preferred embodiments of a power generation system and operating methodfor a fuel cell in the power generation system according to the presentinvention will be described below in detail with reference to thedrawings. The present invention is not limited to the embodiments. Also,when there is a plurality of embodiments, the present invention includesa combination of the plurality of embodiments.

The power generation system according to the first embodiment is theTriple Combined Cycle (registered trademark) in which a solid oxide fuelcell (refers to as “SOFC” below), a gas turbine, and a steam turbine arecombined. The Triple Combined Cycle can generate the power in threestages, i.e., the SOFC, the gas turbine, and the steam turbine, byplacing the SOFC on the side of the upstream of a gas turbine combinedcycle power generation (GTCC). Therefore, an extremely high powergeneration efficiency can be realized. In the description below, thesolid oxide fuel cell is applied as the fuel cell of the presentinvention. However, the fuel cell is not limited to this type.

FIG. 1 is a schematic block diagram of the power generation systemaccording to the first embodiment of the present invention. FIG. 2 is atiming diagram of the power generation system according to the firstembodiment at the time of driving.

In the first embodiment, as illustrated in FIG. 1, a power generationsystem 10 includes a gas turbine 11, a generator 12, a SOFC 13, a steamturbine 14, and a generator 15. The power generation system 10 canobtain a high power generation efficiency by combining power generationby the gas turbine 11, power generation by the SOFC 13, and powergeneration by the steam turbine 14.

The gas turbine 11 has a compressor 20, a first combustor 21A, a secondcombustor 21B, a first turbine 22A, and a second turbine 22B.

The compressor 20 compresses air A taken from an air intake line 24. Thecompressor 20 is shaft-coupled with the first turbine 22A via a rotationshaft 23A, and the compressor 20 and the first turbine 22A can beintegrally rotated.

The first combustor 21A is coupled with the compressor 20 via a firstcompressed air supply line 25 and a first compressed air supply branchline 25A which is one of two lines branched from the first compressedair supply line 25. Then, compressed air A1 is supplied to the firstcombustor 21A from the compressor 20. Also, fuel gas L1 is supplied tothe first combustor 21A through a first fuel gas supply line 26. Thefirst fuel gas supply line (fuel gas supply line) 26 has a first fuelgas control valve (fuel gas control valve) 28 provided therein. Thefirst fuel gas control valve 28 can adjust an amount of air to besupplied. The first combustor 21A mixes the compressed air A1 with thefuel gas L1 and burns it. Here, for example, liquefied natural gas (LNG)is used as the fuel gas L1 to be supplied to the first combustor 21A.The second combustor 21B is coupled with the compressor 20 via the firstcompressed air supply line 25 and a first compressed air supply branchline 25B which is another one of the two lines branched from the firstcompressed air supply line 25. Then, the compressed air A1 is suppliedfrom the compressor 20 to the second combustor 21B. Also, exhausted fuelgas L3 is supplied to the second combustor 21B through an exhausted fuelgas supply line 45 to be described below. The second combustor 21B mixesthe compressed air A1 with the exhausted fuel gas L3 and burns it. Thefirst compressed air supply line 25 has a first compressed air controlvalve 29 provided therein which can adjust the amount of air to besupplied. Also, in the another first compressed air supply branch line25B, a first compressed air branch control valve 30 is provided whichcan adjust the amount of air to be supplied.

The first turbine 22A is rotated by combustion gas G1 supplied from thefirst combustor 21A through a first combustion gas supply line 27A. Thesecond turbine 22B is rotated by combustion gas G2 supplied from thesecond combustor 21B through a second combustion gas supply line 27B.The first turbine 22A and the second turbine 22B are shaft-coupled by arotation shaft 23B so as to be integrally rotated. The rotation shaft23B and the rotation shaft 23A are coaxially arranged. Also, aconnecting/disconnecting unit 60 for connecting/disconnecting the shaftcoupling between the first turbine 22A and the second turbine 22B isprovided on the rotation shaft 23B arranged between the first turbine22A and the second turbine 22B. The connecting/disconnecting unit 60 maybe a clutch.

The compressor 20, the first turbine 22A, and the second turbine 22B arecoaxially provided in the generator 12, and the generator 12 cangenerate the power by rotating the first turbine 22A and the secondturbine 22B.

The high-temperature fuel gas as a reducing agent and high-temperatureair (oxidizing gas) as an oxidant are supplied to the SOFC 13 so thatthey react at a predetermined operating temperature and the SOFC 13generates the power. In the SOFC 13, an air electrode, a solidelectrolyte, and a fuel electrode are contained in a pressure vessel.Compressed air A2 compressed by the compressor 20 is supplied to the airelectrode, and the fuel gas L2 is supplied to the fuel electrode.According to this, the power is generated. Here, for example, liquefiednatural gas (LNG), hydrocarbon gas such as hydrogen (H₂), carbonmonoxide (CO), and methane (CH₄), and gas produced by a gasificationfacility of a carbonaceous material such as coals are used as the fuelgas L2 to be supplied to the SOFC 13. Also, the oxidizing gas to besupplied to the SOFC 13 is gas including about 15% to 30% oxygen.Typically, the air is preferred. However, mixed gas of flue gas and theair, mixed gas of oxygen and the air, and the like other than the aircan be used (the oxidizing gas supplied to the SOFC 13 will be referredto as “air” below).

The SOFC 13 is coupled with the compressor 20 via a second compressedair supply line 31, and a part of the compressed air A2 compressed bythe compressor 20 can be supplied to an introduction unit of the airelectrode. In the second compressed air supply line 31, a secondcompressed air control valve 32 which can adjust the amount of the airto be supplied and a compressed air blower 33 which can boost thecompressed air A2 are provided along a flow direction of the compressedair A2. The second compressed air control valve 32 is provided on theside of the upstream in the flow direction of the compressed air A2 inthe second compressed air supply line 31, and the compressed air blower33 is provided on the side of the downstream of the second compressedair control valve 32. The SOFC 13 is coupled with an air exhaust line 34for exhausting the compressed air A3 used by the air electrode. The airexhaust line 34 is branched into two lines, i.e., an exhausting line 35and a compressed air circulation line 36. The exhausting line 35exhausts the compressed air A3 used by the air electrode to the outside.The compressed air circulation line 36 is coupled to the firstcompressed air supply line 25 in a front side of a branch point of thefirst compressed air supply branch lines 25A and 25B. A compressed airexhaust control valve 37 which can adjust the amount of the air to beexhausted is provided in the exhausting line 35. A compressed aircirculation control valve 38 which can adjust the amount of circular airis provided in the compressed air circulation line 36.

Also, in the SOFC 13, a second fuel gas supply line 41 for supplying thefuel gas L2 to the introduction unit of the fuel electrode is provided.The second fuel gas supply line 41 has a second fuel gas control valve42 provided therein. The second fuel gas control valve 42 can adjust theamount of the fuel gas to be supplied. The SOFC 13 is coupled with anexhausted fuel line 43 for exhausting the exhausted fuel gas L3 used bythe fuel electrode. The exhausted fuel line 43 is branched into anexhausting line 44 for exhausting the exhausted fuel gas L3 to theoutside and the exhausted fuel gas supply line 45 coupled with thesecond combustor 21B. An exhausted fuel gas exhaust control valve 46which can adjust the amount of the fuel gas to be exhausted is providedin the exhausting line 44. An exhausted fuel gas control valve 47 whichcan adjust the amount of the fuel gas to be supplied and an exhaustedfuel gas blower 48 which can boost the exhausted fuel gas L3 areprovided in the exhausted fuel gas supply line 45 along the flowdirection of the exhausted fuel gas L3. The exhausted fuel gas controlvalve 47 is provided on the side of the upstream in the flow directionof the exhausted fuel gas L3 in the exhausted fuel gas supply line 45.The exhausted fuel gas blower 48 is provided on the side of thedownstream of the exhausted fuel gas control valve 47 in the flowdirection of the exhausted fuel gas L3.

Also, a fuel gas re-circulation line 49 for coupling the exhausted fuelline 43 with the second fuel gas supply line 41 is provided. In the fuelgas re-circulation line 49, a re-circulation blower 50 for recirculatingthe exhausted fuel gas L3 in the exhausted fuel line 43 to the secondfuel gas supply line 41 is provided.

A turbine 52 is rotated by steam generated by a heat recovery steamgenerator (HRSG) 51 in the steam turbine 14. A steam supply line 54 anda water supply line 55 are provided between the steam turbine 14(turbine 52) and the heat recovery steam generator 51. A steam condenser56 and a water supply pump 57 are provided in the water supply line 55.The heat recovery steam generator 51 is coupled with a flue gas line 53from the gas turbine 11 (first turbine 22A and second turbine 22B).Steam S is generated by exchanging heat between high-temperature fluegas G3 supplied from the flue gas line 53 and water supplied from thewater supply line 55. The generator 15 and the turbine 52 are coaxiallyprovided, and the power can be generated by rotating the turbine 52. Theheat is recovered from the flue gas G3 by the heat recovery steamgenerator 51. The flue gas G3 is released to the atmosphere afterharmful substances have been removed from the flue gas G3.

A driving method (driving procedure) for the power generation system 10according to the first embodiment will be described with reference toFIGS. 1 and 2. When the power generation system 10 is driven, the gasturbine 11, the steam turbine 14, and the SOFC 13 are driven in thisorder. A control device (controller) 70 generally controls the drive ofthe power generation system 10.

First, the control device 70 opens the first fuel gas control valve 28of the first fuel gas supply line 26 and the first compressed aircontrol valve 29 of the first compressed air supply line 25, and at thesame time, disconnects the connecting/disconnecting unit 60. Then, thecontrol device 70 closes other control valves 30, 32, 37, 38, 42, 46,and 47 and stops the water supply pump 57 and the blowers 33, 48, and50. That is, in the gas turbine 11, air A is compressed by thecompressor 20, and the compressed air A1 and the fuel gas L1 are mixedtogether and burned by the first combustor 21A. Also, in the gas turbine11, the first turbine 22A is rotated by the combustion gas G1. The firstturbine 22A reaches the rated load, and the generator 12 starts togenerate the power.

Subsequently, the control device 70 drives the water supply pump 57.That is, in the steam turbine 14, the turbine 52 is rotated by the steamS generated by the heat recovery steam generator 51, and accordingly,the generator 15 starts to generate the power.

Subsequently, in a state where the compressed air exhaust control valve37 of the exhausting line 35 and the compressed air circulation controlvalve 38 of the compressed air circulation line 36 are closed and thecompressed air blower 33 of the second compressed air supply line 31 isstopped, the control device 70 opens the second compressed air controlvalve 32 of the second compressed air supply line 31 by a predeterminedopening. A part of the compressed air A2 compressed by the compressor 20is supplied from the second compressed air supply line 31 to the side ofthe SOFC 13. According to this, the supply of the compressed air A2increases a pressure on the side of the air electrode of the SOFC 13.That is, in order to drive the SOFC 13, pressurization on the SOFC 13 isstarted by supplying the compressed air A2 from the compressor 20, andat the same time, heating is started.

On the other hand, in a state where the exhausted fuel gas exhaustcontrol valve 46 of the exhausting line 44 and the exhausted fuel gascontrol valve 47 of the exhausted fuel gas supply line 45 are closed andthe exhausted fuel gas blower 48 is stopped, the control device 70 opensthe second fuel gas control valve 42 of the second fuel gas supply line41, and at the same time, drives the re-circulation blower 50 of thefuel gas re-circulation line 49. Then, the fuel gas L2 is supplied fromthe second fuel gas supply line 41 to the SOFC 13, and at the same time,the exhausted fuel gas L3 is recirculated by the fuel gas re-circulationline 49. According to this, the supply of the fuel gas L2 increases apressure on the side of the SOFC 13. That is, the fuel gas L2 issupplied to the side of the fuel electrode of the SOFC 13, andpressurization is started.

An inlet pressure of the compressed air A1 in the first combustor 21Abecomes an outlet pressure of the compressor 20, and a pressure on theside of the air electrode of the SOFC 13 becomes the outlet pressure ofthe compressor 20, and accordingly, the pressures are equalized. At thistime, the control device 70 fully opens the second compressed aircontrol valve 32 and drives the compressed air blower 33 at the sametime. Concurrently, the control device 70 opens the compressed airexhaust control valve 37 and exhausts the compressed air A3, which issupplied from the SOFC 13, from the exhausting line 35. Then, thecompressed air A2 is supplied to the side of the SOFC 13 by thecompressed air blower 33. Concurrently, the control device 70 stops there-circulation blower 50 and opens the exhausted fuel gas exhaustcontrol valve 46. Then, the exhausted fuel gas L3 from the SOFC 13 isexhausted from the exhausting line 44. When the pressure on the side ofthe air electrode and the pressure on the side of the fuel electrode inthe SOFC 13 reaches a target pressure, the pressurization of the SOFC 13is completed.

After that, when reaction (power generation) of the SOFC 13 becomesstable and components, temperatures, and pressure of the compressed airA3 and the exhausted fuel gas L3 become stable (constant), the controldevice 70 closes the first compressed air control valve 29 and thecompressed air exhaust control valve 37 and opens the compressed aircirculation control valve 38. Then, the compressed air A3 from the SOFC13 is supplied from the compressed air circulation line 36 to the firstcombustor 21A through the first compressed air supply branch line 25A.That is, the first turbine 22A is rotated by the combustion gas G1burned in the first combustor 21A by using the compressed air A3 fromthe SOFC 13.

In addition, the control device 70 connects the connecting/disconnectingunit 60 and closes the exhausted fuel gas exhaust control valve 46.Also, the control device 70 opens the first compressed air branchcontrol valve 30 of the first compressed air supply branch line 25B andthe exhausted fuel gas control valve 47 and drives the exhausted fuelgas blower 48. Then, the exhausted fuel gas L3 from the SOFC 13 issupplied from the exhausted fuel gas supply line 45 to the secondcombustor 21B, and at the same time, the compressed air A3 from the SOFC13 is supplied to the second combustor 21B. That is, the second turbine22B is rotated by the combustion gas G2 burned in the second combustor21B by using the compressed air A3 from the SOFC 13 and the exhaustedfuel gas L3 from the SOFC 13.

All the three power generations are performed, i.e., power generation bythe generator 12 by driving the first turbine 22A and the second turbine22B in the gas turbine 11, power generation by the SOFC 13, and powergeneration by the generator 15 by driving the steam turbine 14.Accordingly, the power generation system 10 performs a steady operation.

It is not necessary to provide the connecting/disconnecting unit 60. Inthis case, the first turbine 22A is constantly shaft-coupled with thesecond turbine 22B. When the combustion gas G2 is not supplied to thesecond turbine 22B at the time of driving the first turbine 22A, thesecond turbine 22B and the first turbine 22A are rotated together.

In this way, in the power generation system 10 according to the firstembodiment, the exhausted fuel gas L3 exhausted from the SOFC 13 is usedas a fuel of the combustor of the gas turbine 11, and at the same time,a part of the compressed air A2 compressed by the compressor 20 of thegas turbine 11 is used to drive the SOFC 13. The gas turbine 11 includesthe first combustor 21A for burning the fuel gas L1 which is differentkind from the exhausted fuel gas L3, the first turbine 22A driven by thecombustion gas G1 supplied from the first combustor 21A, the secondcombustor 21B for burning the exhausted fuel gas L3, and the secondturbine 22B shaft-coupled with the first turbine 22A and driven by thecombustion gas G2 supplied from the second combustor 21B.

Therefore, the power generation system 10 according to the firstembodiment separately burns the exhausted fuel gas L3 and the fuel gasL1 in different combustors 21A and 21B. Therefore, it is not necessaryto mix the exhausted fuel gas L3 and the fuel gas L1 by the mixer. Thereis no case where the respective fuel gases L3 and L1 are not evenlymixed and the combustion becomes unstable and where it is necessary totake measures against the thermal expansion in the mixer and the pipingaround the mixer due to the difference in temperature. Accordingly, theinconvenience caused by the difference in temperature of the differentkinds of the fuel gases L3 and L1 can be solved.

Also, the power generation system 10 according to the first embodimentincludes the connecting/disconnecting unit 60 forconnecting/disconnecting a shaft coupling between the first turbine 22Aand the second turbine 22B.

Therefore, when the connecting/disconnecting unit 60 is not included,since the second turbine 22B is rotated together with the first turbine22A in a state where the combustion gas G2 is not supplied to the secondturbine 22B at the time of driving only the first turbine 22A, the loadis applied to the first turbine 22A. However, a situation where the loadis applied to the first turbine 22A can be prevented by having theconnecting/disconnecting unit 60.

Also, the power generation system 10 according to the first embodimentincludes the first fuel gas supply line (fuel gas supply line) 26 forsupplying the fuel gas L1 to the first combustor 21A, the exhausted fuelgas supply line 45 for supplying the exhausted fuel gas L3 to the secondcombustor 21B, the first fuel gas control valve (fuel gas control valve)28 provided in the first fuel gas supply line 26, the exhausted fuel gascontrol valve 47 provided in the exhausted fuel gas supply line 45, andthe control device (controller) 70 for performing control to close theexhausted fuel gas control valve 47 and open the first fuel gas controlvalve 28 before the SOFC 13 is driven and control to open the exhaustedfuel gas control valve 47 after the SOFC 13 has been driven.

Therefore, when the gas turbine 11 is driven, the first turbine 22A isdriven by supplying the fuel gas L1 to the first combustor 21A. Also,after the first turbine 22A has been driven, a part of the compressedair A2 compressed by the compressor 20 is supplied to the SOFC 13, andthe SOFC 13 is driven. When the SOFC 13 is driven, since the exhaustedfuel gas L3 is exhausted from the SOFC 13, the exhausted fuel gas L3 issupplied to the second combustor 21B. In this way, the power generationsystem 10 according to the first embodiment separately burns theexhausted fuel gas L3 and the fuel gas L1 respectively in the differentcombustors 21A and 21B. At the same time, the power generation system 10can efficiently drive the SOFC 13.

Also, the driving method for the power generation system 10 according tothe first embodiment uses the exhausted fuel gas L3 exhausted from theSOFC 13 as a fuel of the combustor of the gas turbine 11 and uses a partof the compressed air A2 compressed by the compressor 20 of the gasturbine 11 to drive the SOFC 13. In the driving method for the powergeneration system 10, the gas turbine 11 includes the first combustor21A for burning the fuel gas L1 which is a different kind from theexhausted fuel gas L3, the first turbine 22A driven by the combustiongas G1 supplied from the first combustor 21A, the second combustor 21Bfor burning the exhausted fuel gas L3, and the second turbine 22Bshaft-coupled with the first turbine 22A and driven by the combustiongas G2 supplied from the second combustor 21B. The driving method forthe power generation system 10 includes a process for supplying the fuelgas L1 to the first combustor 21A and driving the first turbine 22A, aprocess for subsequently driving the SOFC 13, and a process forsubsequently supplying the exhausted fuel gas L3 to the second combustor21B and driving the second turbine 22B.

Therefore, when the gas turbine 11 is driven, the first turbine 22A isdriven by supplying the fuel gas L1 to the first combustor 21A. Also,after the first turbine 22A has been driven, a part of the compressedair A2 compressed by the compressor 20 is supplied to the SOFC 13, andthe SOFC 13 is driven. When the SOFC 13 is driven, since the exhaustedfuel gas L3 is exhausted from the SOFC 13, the exhausted fuel gas L3 issupplied to the second combustor 21B. In this way, the driving methodfor the power generation system 10 according to the first embodimentseparately burns the exhausted fuel gas L3 and the fuel gas L1respectively in the different combustors 21A and 21B. Therefore, it isnot necessary to mix the exhausted fuel gas L3 and the fuel gas L1 bythe mixer. There is no case where the respective fuel gases L3 and L1are not evenly mixed and the combustion becomes unstable and where it isnecessary to take measures against the thermal expansion in the mixerand the piping around the mixer due to the difference in temperature.Accordingly, the inconvenience caused by the difference in temperatureof the different kinds of the fuel gases L3 and L1 can be solved. Inthis way, the driving method for the power generation system 10according to the first embodiment separately burns the exhausted fuelgas L3 and the fuel gas L1 respectively in the different combustors 21Aand 21B. At the same time, the driving method for the power generationsystem 10 can efficiently drive the SOFC 13.

Also, the driving method for the power generation system 10 according tothe first embodiment includes the connecting/disconnecting unit 60 forconnecting/disconnecting the shaft coupling between the first turbine22A and the second turbine 22B. The driving method for the powergeneration system 10 includes a process for disconnecting the shaftcoupling between the first turbine 22A and the second turbine 22B by theconnecting/disconnecting unit 60, a process for subsequently supplyingthe fuel gas L1 to the first combustor 21A and driving the first turbine22A, a process for subsequently driving the SOFC 13, a process forsubsequently connecting the shaft coupling between the first turbine 22Aand the second turbine 22B by the connecting/disconnecting unit 60, anda process for subsequently supplying the exhausted fuel gas L3 to thesecond combustor 21B and driving the second turbine 22B.

Therefore, when the connecting/disconnecting unit 60 is not included,since the second turbine 22B is rotated together with the first turbine22A in a state where the combustion gas G2 is not supplied to the secondturbine 22B at the time of driving only the first turbine 22A, the loadis applied to the first turbine 22A. However, a situation where the loadis applied to the first turbine 22A can be prevented by having theconnecting/disconnecting unit 60.

Second Embodiment

Preferred embodiments of a power generation system and operating methodfor a fuel cell in the power generation system according to the presentinvention will be described below in detail with reference to thedrawings. The present invention is not limited to the embodiments. Also,when there is a plurality of embodiments, the present invention includesa combination of the plurality of embodiments.

The power generation system of the second embodiment is the TripleCombined Cycle (registered trademark) in which a solid oxide fuel cell(refers to as “SOFC” below), a gas turbine, and a steam turbine arecombined. The Triple Combined Cycle can generate the power in threestages, i.e., the SOFC, the gas turbine, and the steam turbine, byplacing the SOFC on the side of the upstream of a gas turbine combinedcycle power generation (GTCC). Therefore, an extremely high powergeneration efficiency can be realized. In the description below, thesolid oxide fuel cell is applied as the fuel cell of the presentinvention. However, the fuel cell is not limited to this type.

FIG. 3 is a schematic diagram of a combustor of a power generationsystem according to a second embodiment of the present invention. FIG. 4is a cross-sectional diagram along the line A-A in FIG. 3. FIG. 5 is aflowchart of fuel supply in the power generation system of the secondembodiment at the time of driving the combustor. FIG. 6 is a schematicblock diagram of the power generation system according to the secondembodiment.

In the second embodiment, as illustrated in FIG. 6, a power generationsystem 110 includes a gas turbine 111, a generator 112, a SOFC 113, asteam turbine 114, and a generator 115. The power generation system 110can obtain a high power generation efficiency by combining powergeneration by the gas turbine 111, power generation by the SOFC 113, andpower generation by the steam turbine 114.

The gas turbine 111 includes a compressor 121, a combustor 122, and aturbine 123. The compressor 121 is coupled with the turbine 123 via arotation shaft 124, and the compressor 121 and the turbine 123 can beintegrally rotated. The compressor 121 compresses air A100 taken from anair intake line 125. The combustor 122 mixes compressed air A101supplied from the compressor 121 through a first compressed air supplyline 126 with fuel gas L101 supplied from a first fuel gas supply line127 and burns it. The turbine 123 is rotated by combustion gas G101supplied from the combustor 122 through a fuel gas supply line 128.Although it is not shown in FIG. 6, the compressed air A101 compressedby the compressor 121 is supplied to the turbine 123 through a housing,and the turbine 123 cools a blade and the like by using the compressedair A101 as cooling air. The generator 112 and the turbine 123 arecoaxially provided, and the power can be generated by rotating theturbine 123. Here, for example, liquefied natural gas (LNG) is used asthe fuel gas L101 to be supplied to the combustor 122.

The high-temperature fuel gas as a reducing agent and high-temperatureair (oxidizing gas) as an oxidant are supplied to the SOFC 113 so thatthey react at a predetermined operating temperature and the SOFC 113generates the power. In the SOFC 113, an air electrode, a solidelectrolyte, and a fuel electrode are contained in a pressure vessel.Compressed air A102 compressed by the compressor 121 is supplied to theair electrode, and the fuel gas L102 is supplied to the fuel electrode.According to this, the power is generated. Here, for example, liquefiednatural gas (LNG), hydrocarbon gas such as hydrogen (H₂), carbonmonoxide (CO), and methane (CH₄), and gas produced by a gasificationfacility of a carbonaceous material such as coals are used as the fuelgas L102 to be supplied to the SOFC 113. Also, the oxidizing gassupplied to the SOFC 113 is gas including about 15% to 30% oxygen.Typically, the air is preferred. However, mixed gas of flue gas and theair, mixed gas of oxygen and the air, and the like other than the aircan be used (the oxidizing gas supplied to the SOFC 113 will be referredto as “air” below).

The SOFC 113 is coupled with a second compressed air supply line 131branched from the first compressed air supply line 126, and a part ofthe compressed air A102 compressed by the compressor 121 can be suppliedto an introduction unit of the air electrode. In the second compressedair supply line 131, a control valve 132 which can adjust the amount ofthe air to be supplied and a blower 133 which can boost the compressedair A102 are provided along a flow direction of the compressed air A102.The control valve 132 is provided on the side of the upstream in theflow direction of the compressed air A102 in the second compressed airsupply line 131, and the blower 133 is provided on the side of thedownstream of the control valve 132. The SOFC 113 is coupled with an airexhaust line 134 for exhausting compressed air A103 used by the airelectrode. The air exhaust line 134 is branched into an exhausting line135 for exhausting the compressed air A103 (exhaust air) used by the airelectrode to the outside and a compressed air circulation line 136coupled with the combustor 122. A control valve 137 which can adjust theamount of the air to be exhausted is provided in the exhausting line135. A control valve 138 which can adjust the amount of circular air isprovided in the compressed air circulation line 136.

Also, in the SOFC 113, a second fuel gas supply line 141 for supplyingthe fuel gas L102 to the introduction unit of the fuel electrode isprovided. The second fuel gas supply line 141 has a control valve 142provided therein. The control valve 142 can adjust the amount of thefuel gas to be supplied. The SOFC 113 is coupled with an exhausted fuelline 143 for exhausting the exhausted fuel gas L103 used by the fuelelectrode. The exhausted fuel line 143 is branched into an exhaustingline 144 for exhausting the exhausted fuel to the outside and anexhausted fuel gas supply line 145 coupled with the combustor 122. Acontrol valve 146 which can adjust the amount of the fuel gas to beexhausted is provided in the exhausting line 144. A control valve 147which can adjust the amount of the fuel gas to be supplied and a blower148 which can boost the exhausted fuel gas L103 are provided in theexhausted fuel gas supply line 145 along the flow direction of theexhausted fuel gas L103. The control valve 147 is provided on the sideof the upstream in the flow direction of the exhausted fuel gas L103 inthe exhausted fuel gas supply line 145. The blower 148 is provided onthe side of the downstream in the flow direction of the exhausted fuelgas L103 of the control valve 147.

Also, a fuel gas re-circulation line 149 for coupling the exhausted fuelline 143 with the second fuel gas supply line 141 is provided in theSOFC 113. In the fuel gas re-circulation line 149, a re-circulationblower 150 for recirculating the exhausted fuel gas L103 in theexhausted fuel line 143 to the second fuel gas supply line 141 isprovided.

A turbine 152 is rotated by steam generated by a heat recovery steamgenerator (HRSG) 151 in the steam turbine 114. A steam supply line 154and a water supply line 155 are provided between the steam turbine 114(turbine 152) and the heat recovery steam generator 151. A steamcondenser 156 and a water supply pump 157 are provided in the watersupply line 155. The heat recovery steam generator 151 is coupled with aflue gas line 153 from the gas turbine 111 (turbine 123). Steam 5100 isgenerated by exchanging heat between high-temperature flue gas G102supplied from the flue gas line 153 and water supplied from the watersupply line 155. The generator 115 and the turbine 152 are coaxiallyprovided, and the power can be generated by rotating the turbine 152.The heat is recovered from the flue gas G102 by the heat recovery steamgenerator 151. The flue gas G102 is released to the atmosphere afterharmful substances have been removed from the flue gas G102.

Here, an operation of the power generation system 110 according to thesecond embodiment will be described. When the power generation system110 is started, the gas turbine 111, the steam turbine 114, and the SOFC113 are started in this order.

First, in the gas turbine 111, the air A100 is compressed by thecompressor 121, and the combustor 122 mixes the compressed air A101 andthe fuel gas L101 and burns it. Also, the turbine 123 is rotated by thecombustion gas G101. Accordingly, the generator 112 starts to generatethe power. Next, the turbine 152 is rotated by the steam 5100 generatedby the heat recovery steam generator 151 in the steam turbine 114, andaccord to this, the generator 115 starts to generate the power.

Subsequently, in order to start the SOFC 113, pressurization on the SOFC113 is started by supplying the compressed air A102 from the compressor121, and at the same time, heating is started. In a state where thecontrol valve 137 of the exhausting line 135 and the control valve 138of the compressed air circulation line 136 are closed and the blower 133of the second compressed air supply line 131 is stopped, the controlvalve 132 is opened by a predetermined opening. A part of the compressedair A102 compressed by the compressor 121 is supplied to the side of theSOFC 113 from the second compressed air supply line 131. According tothis, the supply of the compressed air A102 increases a pressure on theside of the air electrode of the SOFC 113.

On the other hand, the fuel gas L102 is supplied to the side of the fuelelectrode of the SOFC 113, and pressurization is started. In a statewhere the control valve 146 of the exhausting line 144 and the controlvalve 147 of the exhausted fuel gas supply line 145 are closed and theblower 148 is stopped, the control valve 142 of the second fuel gassupply line 141 is opened, and at the same time, the re-circulationblower 150 of the fuel gas re-circulation line 149 is driven. Then, thefuel gas L102 is supplied from the second fuel gas supply line 141 tothe SOFC 113, and at the same time, the exhausted fuel gas L103 isrecirculated by the fuel gas re-circulation line 149. According to this,the supply of the fuel gas L102 increases a pressure on the side of theSOFC 113.

When the pressure on the side of the air electrode of the SOFC 113becomes an outlet pressure of the compressor 121, the control valve 132is fully opened and the blower 133 is driven. At the same time, thecontrol valve 137 is opened, and the compressed air A103 from the SOFC113 is exhausted from the exhausting line 135. Then, the compressed airA102 is supplied to the side of the SOFC 113 by the blower 133. At thesame time, the control valve 146 is opened, and the exhausted fuel gasL103 from the SOFC 113 is exhausted from the exhausting line 144. Whenthe pressure on the side of the air electrode and the pressure on theside of the fuel electrode in the SOFC 113 reach target pressures, thepressurization of the SOFC 113 is completed.

After that, when reaction (power generation) of the SOFC 113 becomesstable and components of the compressed air A103 and the exhausted fuelgas L103 become stable, the control valve 137 is closed and the controlvalve 138 is opened. Then, the compressed air A103 from the SOFC 113 issupplied from the compressed air circulation line 136 to the combustor122. Also, the blower 148 is driven by closing the control valve 146 andopening the control valve 147. Then, the exhausted fuel gas L103 fromthe SOFC 113 is supplied from the exhausted fuel gas supply line 145 tothe combustor 122. At this time, the fuel gas L101 supplied from thefirst fuel gas supply line 127 to the combustor 122 is reduced.

Here, all the three power generations are performed, i.e., powergeneration by the generator 112 by driving the gas turbine 111, powergeneration by the SOFC 113, and power generation by the generator 115 bydriving the steam turbine 114. Accordingly, the power generation system110 performs a steady operation.

The combustor 122 will be described below. The combustor 122 is arrangedin the housing of the turbine 123 (not shown). The compressed air A101compressed by the compressor 121 and the compressed air A103 exhaustedfrom the SOFC 113 are supplied to the housing, and the combustor 122generates the combustion gas G101 by mixing the compressed air A101, thecompressed air A103, and the fuel gas L101 and burning it.

As illustrated in FIGS. 3 and 4, an inner cylinder 102 is supported inan external cylinder 101 in the combustor 122 so as to form an airpassage R at a predetermined interval. The inner cylinder 102 is coupledwith a transition piece (combustion gas supply line 128). A front endpart of the transition piece is connected to the turbine 123.

In the inner cylinder 102, a pilot nozzle 103 is arranged on a combustoraxis C, which is the central part of the inner cylinder 102, along anextending direction of the combustor axis C. The pilot nozzle 103 has acombustion chamber 103 b mounted around the front end part thereof. Thecombustion chamber 103 b has a cylindrical shape, and the side of thefront end has a wider angle.

Also, in the inner cylinder 102, a plurality of (eight in the secondembodiment) main nozzles 104 (also referred to as “premixing nozzle”) isarranged in parallel to the combustor axis C so as to surround the pilotnozzle 103 along the circumferential direction of the inner surface inthe inner cylinder 102. The main nozzles 104 include first main nozzles104A and second main nozzles 104B. In the second embodiment, four firstmain nozzles 104A and four second main nozzles 104B are provided, andthe first and second main nozzles 104A and 104B are alternately arrangedin the circumferential direction of the inner cylinder 102.

A top hat part 101A is provided in a base end part of the externalcylinder 101. The top hat part 101A includes a cylindrical member 101Aaand a lid member 101Ab. The cylindrical member 101Aa is arranged alongthe inner surface of the base end part of the external cylinder 101 andforms a part of the air passage R together with the external cylinder101. The lid member 101Ab closes an opening of the cylindrical member101Aa on the side of the base end. The lid member 101Ab supports theabove-mentioned pilot nozzle 103, and a fuel port 103 a of the pilotnozzle 103 is arranged outside the lid member 101Ab. The fuel port 103 ais connected to a pilot nozzle fuel line 127 a branched from the firstfuel gas supply line 127, the fuel gas L101 is supplied to the pilotnozzle 103. Also, the lid member 101Ab supports the above-mentionedfirst main nozzle 104A and second main nozzle 104B, and a fuel port104Aa of the first main nozzle 104A and a fuel port 104Ba of the secondmain nozzle 104B are arranged outside the lid member 101Ab. The fuelport 104Aa of the first main nozzle 104A is connected to the exhaustedfuel gas supply line 145 as a first main nozzle fuel line, and theexhausted fuel gas L103 is supplied to the first main nozzle 104A. Also,the fuel port 104Ba of the second main nozzle 104B is connected to asecond main nozzle fuel line 127 b branched from the first fuel gassupply line 127, and the fuel gas L101 is supplied to the second mainnozzle 104B.

Also, a pilot nozzle control valve 105A for controlling the supply ofthe fuel gas L101 to the pilot nozzle 103 is provided in the pilotnozzle fuel line 127 a. Also, a first main nozzle control valve 105B forcontrolling the supply of the exhausted fuel gas L103 to the first mainnozzle 104A is provided in the exhausted fuel gas supply line 145. Also,a second main nozzle control valve 105C for controlling the supply ofthe fuel gas L101 to the second main nozzle 104B is provided in thesecond main nozzle fuel line 127 b.

In this combustor 122, when high-temperature and high-pressurecompressed air A101 and compressed air A103 flow into the air passage Rfrom the top end side of the external cylinder 101, the compressed airA101 and the compressed air A103 return at a position of the top hatpart 101A on the side of the base end of the external cylinder 101 andflow into the inner cylinder 102. In the inner cylinder 102, the fuelgas L101 and the exhausted fuel gas L103 injected from the main nozzles104 (104A and 104B) are mixed with the compressed air A101 and thecompressed air A103 for flowing into the inner cylinder 102, and theybecome the premixed gas. The premixed gas flows into the transitionpiece on the side of the top end of the inner cylinder 102. Also, in theinner cylinder 102, the fuel gas L101 injected from the pilot nozzle 103is mixed with the compressed air A101 and the compressed air A103 forflowing into the inner cylinder 102, and it is ignited by a pilot lightwhich is not shown and burned. Then, the combustion gas G101 isgenerated and injected into the transition piece. At this time, a partof the combustion gas G101 is injected into the transition piece withflame so as to be diffused to the circumference. According to this, thepremixed gas flowing from each main nozzle 104 into the transition pieceis ignited and burned. The generated combustion gas G101 is supplied tothe turbine 123.

In the combustor 122, a control device (controller) 106 controls toopen/close of the respective control valves 105A, 105B, and 105C andcontrols the opening of the valves. The control device 106 controls therespective control valves 105A, 105B, and 105C according to start up andan operation state of the gas turbine 111 and an operation state of theSOFC 113. Therefore, the control device 106 inputs operation states ofthe gas turbine 111 and the SOFC 113 and continuously monitors them.

A driving method for the power generation system 110 according to thesecond embodiment which is the control by the above-mentioned controldevice 106 will be described below. Here, the drive of the gas turbine111 in a case where the gas turbine 111, the steam turbine 114, and theSOFC 113 are started in this order will be described.

First, in a stopped state before the gas turbine 111 is started, thecontrol device 106 closes the pilot nozzle control valve 105A, the firstmain nozzle control valve 105B, and the second main nozzle control valve105C.

As illustrated in FIG. 5, when an instruction to start the gas turbine111 has been received (step S1: Yes), the control device 106 controls toopen the pilot nozzle control valve 105A and the second main nozzlecontrol valve 105C (step S2). The fuel gas L101 is injected from thepilot nozzle 103 by the combustor 122, and the fuel gas L101 is injectedfrom the second main nozzle 104B. Then, the combustor 122 mixes the fuelgas L101 with the compressed air A101 and generates the combustion gas.Accordingly, the gas turbine 111 is started by the combustion gas G101generated from the fuel gas L101.

After that, a part of the compressed air A102 compressed by thecompressor 121 of the gas turbine 111 is supplied to the SOFC 113, andthe fuel gas L102 is supplied to the SOFC 113. Accordingly, the SOFC 113is started. When a signal indicating that the SOFC 113 has been startedhas been input (step S3: Yes), the control device 106 controls to openthe first main nozzle control valve 105B and to restrict the second mainnozzle control valve 105C by a predetermined opening while opening thepilot nozzle control valve 105A (step S4). Then, in the combustor 122,the exhausted fuel gas L103 is injected from the first main nozzle 104A,and the combustion gas G101 is generated. The predetermined opening ofthe second main nozzle control valve 105C is an opening to supplementshortage of the heat input by the exhausted fuel gas L103 relative tothe heat input in which the gas turbine 111 reaches the rated load withthe heat input by supplying the fuel gas L101. According to this, whenthe exhausted fuel gas L103 is exhausted from the SOFC 113 after theSOFC 113 has been started, the gas turbine 111 is mainly driven by theexhausted fuel gas L103. Before the signal indicating that the SOFC 113has been started is input in step S3 (step S3: No), the control device106 opens the pilot nozzle control valve 105A and the second main nozzlecontrol valve 105C in step S2. The combustor 122 generates thecombustion gas G101 by the fuel gas L101 injected from the pilot nozzle103. That is, the gas turbine 111 is driven by the combustion gas G101generated by the fuel gas L101 before the SOFC 113 is started.

In this way, the power generation system 110 uses the exhausted fuel gasL103 to be exhausted from the SOFC 113 as a fuel of the combustor 122 ofthe gas turbine 111. The power generation system 110 according to thesecond embodiment includes the combustor 122, the first main nozzle104A, the second main nozzle 104B, the exhausted fuel gas supply line(first main nozzle fuel line) 145 which is connected to the first mainnozzle 104A and sends the exhausted fuel gas L103 exhausted from theSOFC 113, the second main nozzle fuel line 127 b which is connected tothe second main nozzle 104B and sends the fuel gas L101 different fromthe exhausted fuel gas L103, the first main nozzle control valve 105Bprovided in the exhausted fuel gas supply line 145, and the second mainnozzle control valve 105C provided in the second main nozzle fuel line127 b. The power generation system 110 also includes the control device106 which controls to close the first main nozzle control valve 105B andto open the second main nozzle control valve 105C when the gas turbine111 is started and controls to open the first main nozzle control valve105B and to strict the second main nozzle control valve 105C when theSOFC 113 is started after the gas turbine 111 has been started.

Therefore, when the gas turbine 111 is started, the gas turbine 111 isstarted by supplying the fuel gas L101 to the combustor 122. Also, afterthe gas turbine 111 has been started, a part of the compressed air A102compressed by the compressor 121 is supplied to the SOFC 113, and theSOFC 113 is started. When the SOFC 113 is started, the exhausted fuelgas L103 is exhausted from the SOFC 113. The exhausted fuel gas L103 issupplied to the combustor 122, and at the same time, a predeterminedamount of the fuel gas L101 of which a flow rate is restricted issupplied. In this way, the heat input shortage of the exhausted fuel gasL103 is supplemented. Therefore, the power generation system 110according to the second embodiment can drive the gas turbine 111 in astable state. In addition, since high-temperature (about 450° C.)exhausted fuel gas L103 and low-temperature (about 15° C.) fuel gas L101are separately supplied from the first main nozzle 104A and the secondmain nozzle 104B and burned, a mixer for mixing the exhausted fuel gasL103 with the fuel gas L101 having different temperatures from eachother and supplying it to the combustor 122 can be omitted.

Also, in the power generation system 110 according to the secondembodiment, the combustor 122 includes the pilot nozzle 103, the pilotnozzle fuel line 127 a which is connected to the pilot nozzle 103 andsends the fuel gas L101, and the pilot nozzle control valve 105Aprovided in the pilot nozzle fuel line 127 a. The control device 106controls to open the pilot nozzle control valve 105A when starting ordriving the gas turbine 111.

Therefore, when the gas turbine 111 is started and driven, the fuel gasL101 injected from the pilot nozzle 103 is burned. According to this,flame holding can be performed to perform stable combustion of thepremixed gas in which the exhausted fuel gas L103 and the fuel gas L101respectively injected from the first main nozzle 104A and the secondmain nozzle 104B is mixed with the compressed air.

Also, in the driving method for the power generation system 110according to the second embodiment, the exhausted fuel gas L103exhausted from the SOFC 113 is used as a fuel of the combustor 122 ofthe gas turbine 111. The combustor 122 includes the first main nozzle104A for injecting the exhausted fuel gas L103 exhausted from the SOFC113 and the second main nozzle 104B for injecting the fuel gas L101which is a different kind from the exhausted fuel gas L103. The drivingmethod for the power generation system 110 includes a process forinjecting the fuel gas L101 from the second main nozzle 104B when thegas turbine 111 is started and a process for injecting the exhaustedfuel gas L103 from the first main nozzle 104A and injecting the fuel gasL101 restricted by a predetermined amount from the second main nozzle104B when the SOFC 113 is started after the gas turbine 111 has beenstarted.

Therefore, when the gas turbine 111 is started, the gas turbine 111 isstarted by injecting the fuel gas L101 from the second main nozzle 104Bof the combustor 122 and burning it. Also, after the gas turbine 111 hasbeen started, a part of the compressed air A102 compressed by thecompressor 121 is supplied to the SOFC 113, and the SOFC 113 is started.When the SOFC 113 is started, the exhausted fuel gas L103 exhausted fromthe SOFC 113 is injected from the first main nozzle 104A of thecombustor 122, and at the same time, a predetermined amount of the fuelgas L101 which supplements the heat input shortage of the exhausted fuelgas L103 is injected from the second main nozzle 104B. Therefore, thepower generation system 110 according to the second embodiment can drivethe gas turbine 111 in a stable state. In addition, sincehigh-temperature (about 450° C.) exhausted fuel gas L103 andlow-temperature (about 15° C.) fuel gas L101 are separately suppliedfrom the first main nozzle 104A and the second main nozzle 104B andburned, a mixer for mixing the exhausted fuel gas L103 with the fuel gasL101 having different temperatures from each other and supplying it tothe combustor 122 can be omitted.

Also, the combustor 122 according to the second embodiment, which isincluded in the power generation system 110 having the SOFC 113 and thegas turbine 111, supplies the combustion gas in which the exhausted fuelgas L103 exhausted from the SOFC 113 is burned to the gas turbine 111.The combustor 122 includes the first main nozzle 104A for injecting theexhausted fuel gas L103 exhausted from the SOFC 113, the second mainnozzle 104B for injecting the fuel gas L101 which is different kind fromthe exhausted fuel gas L103, the first main nozzle control valve 105Bfor controlling injection of the exhausted fuel gas L103 from the firstmain nozzle 104A, and the second main nozzle control valve 105C forcontrolling injection of the fuel gas L101 from the second main nozzle104B.

Therefore, when the gas turbine 111 is started, the gas turbine 111 isstarted by opening the second main nozzle control valve 105C, injectingthe fuel gas L101 from the second main nozzle 104B, and burning it.Also, after the gas turbine 111 has been started, a part of thecompressed air A102 compressed by the compressor 121 of the gas turbine111 is supplied to the SOFC 113, and the SOFC 113 is started. When theSOFC 113 is started, the first main nozzle control valve 105B is openedand the exhausted fuel gas L103 exhausted from the SOFC 113 is injectedfrom the first main nozzle 104A and burned, and at the same time, apredetermined amount of the fuel gas L101 of which the flow rate isrestricted by the second main nozzle control valve 105C is injected.Accordingly, the heat input shortage of the exhausted fuel gas L103 issupplemented. Therefore, the power generation system 110 according tothe second embodiment can drive the gas turbine 111 in a stable state.In addition, since high-temperature (about 450° C.) exhausted fuel gasL103 and low-temperature (about 15° C.) fuel gas L101 are separatelysupplied from the first main nozzle 104A and the second main nozzle 104Band burned, a mixer for mixing the exhausted fuel gas L103 with the fuelgas L101 having different temperatures from each other and supplying itto the combustor 122 can be omitted.

Also, the combustor 122 according to the second embodiment furtherincludes the pilot nozzle 103 for injecting the fuel gas L101 and thepilot nozzle control valve 105A for controlling the injection of thefuel gas L101 from the pilot nozzle 103.

Therefore, when the gas turbine 111 is started and driven, the fuel gasL101 injected from the pilot nozzle 103 is burned by opening the pilotnozzle control valve 105A. Accordingly, the flame holding can beperformed to perform the stable combustion of the premixed gas in whichthe exhausted fuel gas L103 and the fuel gas L101 respectively injectedfrom the first main nozzle 104A and the second main nozzle 104B aremixed with the compressed air.

REFERENCE SIGNS LIST

-   -   10 power generation system    -   11 gas turbine    -   12 generator    -   13 SOFC (fuel cell)    -   14 steam turbine    -   15 generator    -   20 compressor    -   21A first combustor    -   21B second combustor    -   22A first turbine    -   22B second turbine    -   26 first fuel gas supply line (fuel gas supply line)    -   28 first fuel gas control valve (fuel gas control valve)    -   45 exhausted fuel gas supply line    -   47 exhausted fuel gas control valve    -   60 connecting/disconnecting unit    -   70 control device    -   103 pilot nozzle    -   104A first main nozzle    -   104B second main nozzle    -   105A pilot nozzle control valve    -   105B first main nozzle control valve    -   105C second main nozzle control valve    -   106 control device (controller)    -   110 power generation system    -   111 gas turbine    -   113 SOFC (solid oxide fuel cell: fuel cell)    -   122 combustor    -   127 a pilot nozzle fuel line    -   127 b second main nozzle fuel line    -   145 exhausted fuel gas supply line (first main nozzle fuel line)    -   L101 fuel gas    -   L103 exhausted fuel gas

1-5. (canceled)
 6. A power generation system comprising: a controllerconfigured to control to close a first main nozzle control valve andopen a second main nozzle control valve when a gas turbine is startedand control to open the first main nozzle control valve and restrict thesecond main nozzle control valve when a fuel cell is started after thegas turbine has been driven, wherein exhausted fuel gas exhausted fromthe fuel cell is used as a fuel of a combustor of the gas turbine, andthe combustor includes a first main nozzle, a second main nozzle, afirst main nozzle fuel line which is connected to the first main nozzleand sends the exhausted fuel gas exhausted from the fuel cell, a secondmain nozzle fuel line which is connected to the second main nozzle andsends a fuel gas different kind from the exhausted fuel gas, the firstmain nozzle control valve provided in the first main nozzle fuel line,and the second main nozzle control valve provided in the second mainnozzle fuel line.
 7. The power generation system according to claim 6,wherein the combustor includes a pilot nozzle, a pilot nozzle fuel linewhich is connected to the pilot nozzle and sends the fuel gas, and apilot nozzle control valve provided in the pilot nozzle fuel line, andthe controller controls to open the pilot nozzle control valve when thegas turbine is started and driven. 8-10. (canceled)